1. Field of the Invention
The present invention relates to a system and method for clamping, engaging and disengaging conduit connections in oil and gas wellhead risers, wherein the wellhead equipment of the well is positioned below the surface of the water.
2. Description of Related Art
In subsea drilling operations, as in any drilling operation, drilling fluid must be circulated through the drill bit in order to cool the bit, carry away the cuttings and provide hydrostatic head pressure against the formation to aid in the prevention of blowouts. This drilling fluid is normally returned to the floating vessel by means of a large diameter pipe, known as a riser, which extends between the subsea wellhead assembly and the floating vessel or rig at the water's surface. The lower end of this riser is connected to the BOP and wellhead assembly which is generally located adjacent the ocean floor, and the upper end usually extends through a centrally located opening of the floating vessel or fixed rig. A drill string extends downward through the riser into earth formations lying below the body of water, and drilling fluids circulate downwardly through the drill string, out through the drilling bit, and then upwardly through the annular space between the drill string and the riser, returning to the vessel or rig.
Buoyancy or ballasting devices may be attached to the submerged portion of the riser. These devices may be comprised of syntactic foam attached on the outer elements of the riser section. These buoyancy devices create upwardly directed forces in the riser, compensating for the compressive stresses created by the riser's weight preventing riser failure.
In an underwater drilling rig riser, multiple lines are integrated in the rig riser. These include multiplexed hydraulic lines, choke lines, boost lines and an Installation/Workover Control Systems (IWOCS) line. In conventional installations, the failure of a riser or its release from the subsea installation due to tripping of a blowout preventer cuts these various lines as they are integrated in the riser. The present invention presents an improved riser clamp to securely hold the various lines in place as well as allowing for the selective release of the all important IWOCS line away from the riser for easy replacement or continued control of the subsurface wellhead assembly.